High-speed processing of an IC tends to increase a heating value. On the other hand, the IC has to be key at or below a certain temperature because of the IC's inner material and other characteristics. When the IC's heating value becomes a prescribed level or higher, release of heat from the IC surface requires a lot of cooling air commensurate with the heating value due to the limited heating surface area.
Therefore, it is necessary to have an expanded heating surface area in order to increase the heating surface area in contact with the cooling air. Various type of heat sinks have been devised as a method for attaining an expanded heating surface area. However, a conventional heat sink shape is limited to whatever shape it may have. On the other hand, there is literature reporting fine pin fins which further improve the radiating performance of a conventional heat sink.
Specifically, the shape of a heat sink to deal with the increase of a heating value in the future is limited, if the conventional shape is continued. Conventional devices are now designed to have a new shape so as to provide very small fins. In using a heat sink having such a finely made shape, the following problems take occur:
(1) Since the fin section of the heat sink is finely worked, if an external force is applied to the finely worked fin section when handling the heat sink (e.g., installation of the heat sink, test, maintenance or transportation of a device or unit equipped with the heat sink), the fin section is readily deformed, requiring very gentle handling. Thus, this design has a disadvantage that workability is degraded.
In addition, if the heat sink is deformed, the flow of a cooling air is changed and the cooling capacity is degraded.
Furthermore, from an opposite viewpoint, when workability is given priority, the finely worked fins of a heat sink cannot be used, also resulting in limited cooling capacity.
(2) Sealing of the circumference of a finely worked section could not be adopted because of clogging due to dust.
(3) In an area of a printed circuit board where high-heat generating ICs are mounted, other parts are also mounted and connected mutually to form the printed circuit board. However, cooling is mainly performed by cooling the printed circuit board as a whole. This is because it is often necessary to cool the parts other than the high-heat generating ICs.
When the air is delivered to cool the whole circuit board, however, the above-described finely worked heat sink has a disadvantage that it has a high air resistance and the cooling air does not flow.